Дана матрица. Упорядочить ее строки по убыванию первых элементов строк — Pascal(Паскаль)

uses crt;
var a:array[1..100,1..100] of integer;
    i,j,n,m,k,x:integer;
begin
ClrScr;
Randomize;
Write('n=');
Readln(n);
Write('m=');
Readln(m);
for i:=1 to n do
 begin
  for j:=1 to m do
   begin
    a[i,j]:=random(20)-10;
    Write(a[i,j]:4);
   end;
  Writeln;
 end;
Writeln;
k:=1;
for i:=1 to n do
for j:=1 to m do
for k:=j to n do
 if a[i,j]<a[i,k] then
  begin
   x:=a[i,j];
   a[i,j]:=a[i,k];
   a[i,k]:=x;
  end;
for i:=1 to n do
 begin
  for j:=1 to m do
   Write(a[i,j]:4);
   Writeln;
 end;
Readln;
end.